The practical purpose of the study on human thermal regulation during space operation is to scientifically justify an automatic thermal control system (ATCS). The primary goal of the ATCS is to maintain the thermal comfort during all possible types of human activities in the most fiendly way. The main purpose of ATCS development is the identification of physiologically valuable requirements and validation of optimal laws used to control human thermal status in the suited mode. Such an identification is possible if we have a good knowledge of the control aim and current thermal status. That means that one needs to a criterion for or an assessment of interrelationship between thermal status, activities and disturbances. The model of human thermal regulation and metabolism in a space suit with a ventilation loop and a water cooling loop is a theoretical basis for ATCS experimental tests. Our model has two interdependent parts: 1) anatomical/physiological compartment and 2) technical compartment. The first part is presented by a cylindrical human body simulator that has a core and skin layers. The skin is divided into two ventilated areas with cooling tubes or without them. The physiological compartment includes such mechanisms as perspiration, vasomotor reactions and heat production, the technical compartment includes a liquid cooling garment (LCG), a gas ventilation loop and a space enclosure. It is represented by a multi-layered envelope used to isolate human from environments. This paper presents a functional scheme of man rated tests to be run to identify and validate model parameters determined by analytical techniques. The paper also presents algorithms and block diagrams of the linear model for a theoretical synthesis in the ATCS context.